1. Field of the Invention
This invention concerns a system for the permanent storage of radioactive wastes and of wastes in general involving a great risk of environmental and human contamination.
To be more exact, the invention concerns a system providing levels of protection against the radioactive material which are functional according to the degree of danger involved by that material, the protection being ensured in the long term even in the event of natural disasters.
2. Discussion of Prior Art
The system of the invention can be applied to sites and terrains of any nature and disposition.
The state of the art includes a plurality of methods and devices for the disposal of toxic and/or radioactive wastes.
Such wastes and, in particular, the radioactive wastes to which we shall refer in the description hereinafter are collected in specific drums or other suitable means having appropriate shapes and sizes.
A plurality of these drums is stacked in turn in an organized manner within storage containers.
Documents IT 83461 A/86 and IT 83413 A/87 in the name of the same applicant describe containers which consist advantageously of high-density centrifuged concrete and are suitable to hold toxic and radioactive wastes.
IT 83413 A/87 cited above discloses also some solutions for the storage of such containers in sites equipped for the purpose, but these solutions may be suitable for temporary, but not permanent, storage of radioactive material.
The most widespread solution nowadays for the permanent storage of radioactive material of medium and low activity consists in placing the containers within stores formed with buried concrete constructions, which are covered with a plurality of layers of clay or another suitable material compacted by mechanical means.
This compacting cannot ensure complete homogeneity of the clay barriers, and this leads to a non-impermeable, imperfect barrier which is not proof against aggressive substances.
In particular, rain water and water from strata lying higher than the stores may develop preferred routes in the long term and arrive within the stores, in conjunction also with possible natural movements of the ground, of a telluric kind for instance, with a grave danger for the airtight seal of the containers themselves.
EP-A-0245912 discloses an underground barrier structure for wastes. The structure consists of a first container within which the waste is deposited and which consists of walls made of a carbonaceous material. A second series of walls is formed of zeolite, and a third series consists of clay. The structure described in EP '912 is not suitable to ensure an efficient degree of protection, especially for radioactive wastes.
WO-A-8400637 describes a storage structure for wastes of various kinds. The structure provides an inner container for the wastes and an outer protective container; a water barrier separates the two containers. The structure described in WO '637 provides for temporary storage of wastes; in fact, access to the inner container is possible. The structure is therefore not suitable for radioactive wastes, as is shown by the use of water as a protective means.
The present applicant has designed a system for the permanent storage of radioactive wastes which is able to overcome the problems of the state of the art.